Liquid crystal display device needs to use a backlight module to illuminate the liquid crystal display panel to control the brightness level of the image. Due to the restrictions of current liquid crystal display panel in technical and the principle, there are still some light from the backlight module will pass through the liquid crystal display panel to form the so-called “dark-state light leakage” when the liquid crystal display panel is in dark state, and therefore the contrast of the liquid crystal display device is reduced.
In order to improve the contrast of the liquid crystal display device, the prior art has developed a backlight module having a local dimming function. According to the illumination direction of the light source, the backlight modules can be divided into three types: direct-illumination type, edge-illumination type and mixing-illumination type.
The direct-illumination type backlight module disposes a plurality group of light sources below the liquid crystal display panel and has the advantage of multi local dimming. However, a certain light mixing chamber is required and therefore the thickness of the direct-illumination type backlight module is relatively large.
The edge-illumination type backlight module disposes the light sources around the liquid crystal display panel and has the advantage of smaller thickness. However, the edge-illumination type backlight module has less local dimming due to the restriction in the design of the light guide plate.
The mixing-illumination type backlight module divides the light guide plate into a plurality of blocks or areas with a plurality group of corresponding light sources and therefore has the advantages of multi local dimming of the direct-illumination type backlight module and the smaller thickness of the edge-illumination type backlight module. However, since the area between the light source and the light guide plate is located in the display area of the liquid crystal display panel, uneven brightness may occur.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.